Different procedures can be utilized to trace errors in sequences of message words of the kind mentioned above. One possibility is to run the sequence it is desired to examine separately with the other sequences in the equipment being stopped during this time, all transmitted values are then registered and errors discovered by writing out and examining all messages in the examined sequence. In this case, the examination result can however be affected by all the other sequences normally progressing parallel thereto being inhibited during the test sequence, so that should an error in the examined sequence originate from the action of another sequence progressing parallel to it, it may happen that the check does not give any result.
Another possibility is to register and write out all sequences, the written-out list being visually examined. This method is very time-consuming, however.